Arel <-> SQL syntax reference

[nimmolo]

This is to provide references and examples of how to rephrase SQL statements in AREL, which seems like a desirable intermediate step to making MO database-agnostic. Although there's a bit of a learning curve, i eventually felt it's not that hard to translate between the two. Those with a firmer understanding of query language may find it easier; on the other hand some of our queries may be more work to rephrase than i'm expecting.

First, some links. I personally needed a bit of handholding to get my head around what exactly Arel does, so others may find some of the latter links a bit verbose.

Composable Query Builders in Rails with Arel - For me, the clearest intro

Source code of Rails Arel Predications - Reference for query "prepositions" in AREL straight from the Rails GitHub repo

Queries on Rails - Active Record and Arel (2020) - Covers most use cases, I believe. very good
Composable SQL Queries in Rails Using Arel - Long but explanatory
How can you do a conditional where clause using AREL - StackOverflow q&a for the specific question I was dealing with in GraphQL, for filtered search
How to build complex queries using Arel - Considering the title, ironically the briefest of these

I'd like to follow up with specific examples of SQL/AREL query syntax.